In this Aug. 14, 2003, file photo a couple enjoys a candlelight dinner at a downtown Toronto restaurant during a major power failure.

Written by

Johathan Fahey
and Kantele Franko

The U.S. electrical grid is better managed and more flexible a decade after its largest blackout but remains vulnerable to increasingly extreme weather, cybersecurity threats, and stress caused by shifts in where and how power is produced.

Many worry the grid isn't fully prepared for the new and emerging challenges, even though an analysis conducted for The Associated Press shows maintenance spending has steadily increased since North America's largest blackout.

"This job of reliability is kind of impossible, in the sense that there's just so many things that could happen that it's ...